Analysis of cell-process induced changes in multicrystalline silicon

We analyse the effect of individual process steps on the material quality of mc-Si wafers. In addition to the commonly used recombination lifetime, we measure material parameters such as the concentration of interstitial oxygen, and of FeB. We show that such additional variables in the analysis can give much more information and insight into the effect of individual process steps. We have processed ingots from several manufacturers using a fired-through silicon nitride passivation scheme, and analysed several variations of process steps. Main results include i) the temperature dependence of phosphorus gettering; ii) the absence of a clear synergetic effect of co-firing silicon nitride with an aluminium rear side coating; and iii) influence of phosphorus diffusion on subsequent hydrogen passivation.